The introduction by Kohler and Millstein in 1975 of a revolutionary new procedure for the routine production of monoclonal antibodies using hybridomas allows the production of almost unlimited quantities of antibodies of precise and reproducible specificity. While conventional antisera produced by immunizing animals with tumor cells or other antigens contain a myriad of different antibodies differing in their specificity and properties, hybridomas produce a single antibody with uniform characteristics. The Kohler-Millstein procedure entails the fusion of spleen cells from an immunized animal with an immortal myeloma cell line. From the fused cells (hybridomas), clones are selected that produce antibody of the desired specificity. As hybridoma cells can be cultured indefinitely (or stored frozen in liquid nitrogen), a constant supply of antibody is assured.
Antibodies are proteins that have the ability to combine with and recognize other molecules, known as antigens. Monoclonal antibodies are not different from other antibodies except that they are very uniform in their properties and recognize only one antigen or a portion of an antigen known as a determinant.
In the case of cells, the determinant recognized is an antigen on or in the cell which reacts with the antibody. It is through these cell antigens that a particular antibody recognizes, i.e., reacts with, a particular kind of cell. Thus the cell antigens are markers by which the cell is identified.
Antigenic markers may be used to observe normal processes of cell differentiation and to locate abnormalities, such as cancer, within a given cell system. The process of differentiation is accomplished by changes in the surface antigenic phenotype, and antigens that distinguish cells at different phases, or transformed cells, may be observed if a correct antibody is available.
Transformation of normal cells into carcinogenic tumor cells is accompanied by changes in surface protein phenotypes. Monoclonal antibodies specific for surface proteins of carcinogenic cells may be used to identify those cells. Additionally, different cancers exhibit different surface protein phenotypes. Hence, it is possible to determine the presence of a particular type of cancer, given the proper monoclonal antibodies.
By means of the monoclonal antibodies of this invention, it is possible to identify choriocarcinoma and teratocarcinoma cells and tissues, utilizing the specificity of monoclonal antibodies to the cell surface markers of these carcinogenic cells and tissues. Choriocarcinomas are cancers which result from transformation of trophoblasts (in the case of gestational choriocarcinomas) or from transformation of germ cells (in the case of germ cell tumors). The transformation alters the surface antigens of the resulting choriocarcinoma, enabling one to distinguish between cancerous and non-cancerous materials.
Panels of monoclonal antibodies are provided which phenotypically identify choriocarcinoma and teratocarcinoma cells and tissues.